Improve Raspberry Pi steps (replaces #325, #326, #30)

[mildsunrise]

• add missing dependencies and autoreconf as mentioned in added autoconf to apt install requirements (RPi) #326 (comment)
• add reboot step so that makefiles and modinfo work as expected
• there's now an iw dev <...> interface add command which deduces the phy, so you can just do:
  iw dev wlan0 interface add mon0 type monitor
• ifconfig may be removed at some point, replaced with ip link equivalent
• mention that the driver needs to be rebuilt / installed after kernel upgrades
• on recent raspbians, it's better to prevent dhcpcd from messing with wlan0 at all (this also prevents wpa_supplicant from running)